Harper, Benjamin, Grace and Victoria share the same hobby of collecting pens. The average number of pens collected by the 4 friends is 23. Benjamin collected 6 more pens than Grace but 13 fewer pens than Harper. Victoria collected 5 pens fewer than Grace. Find the average number of pens collected by Benjamin and Victoria. Round off your answer to the nearest whole number.
Number of pens Grace collected = 1 u
Number of pens Benjamin collected = 1 u + 6
Number of pens Harper collected = 1 u + 6 + 13 = 1 u + 19
Number of pens Victoria collected = 1 u - 5

Total number of pens collected
= 4 x 23
= 92

Total number of pens collected in units
= 1 u + 1 u + 6 + 1 u + 19 + 1 u - 5
= 4 u + 20

4 u + 20 = 92
4 u = 92 - 20 = 72

1 u = 72 ÷ 4 = 18

Total number of pens collected by Benjamin and Victoria
= 1 u + 6 + 1 u - 5
= 2 u + 1
= 2 x 18 + 1
= 37

Average number of pens collected by Benjamin and Victoria
= 37 ÷ 2
≈ 19 (Round off to the nearest whole number.)

Answer(s): 19